There is no clear, universally acceptable definition of asthma. Definitions have been offered by a variety of expert groups (Table 1), but none is sufficiently precise to allow asthmatic subjects to be distinguished from nonasthmatic subjects, based on the definition alone. Indeed, 2 of the 4 definitions listed in Table 1 consider asthma a condition, not a disease. All 4 definitions have as their central criteria a physiologic phenomenon: reversible bronchospasm or increased airway responsiveness. In none of these definitions, however, is the degree of airway responsiveness considered except in the vaguest of terms, eg, “a level or intensity not inducing such narrowing in most individuals.” Thus, there are no operational criteria for implementing any of these definitions in practical terms, and investigators are left to their own devices in integrating these definitions.
Samet emphasized these difficulties by reviewing a year s worth of articles appearing in the American Review of Respiratory Disease in 1983. He found 23 articles referring to asthma. Only 5 of the 23, or 22%, mentioned the ATS criteria. None of the articles provided criteria for meeting this definition. A clinical diagnosis was used in 9 of the 23 articles, or 39%. The components of a clinical diagnosis noted by the authors included symptoms, Canadian medications, allergic status, and physician diagnosis, however teleologic this last criterion might be. Both bronchial responsiveness testing and a clinical history were required criteria in only 4 of the 23 articles, or 17%; and no criteria were given in 5 of the 23, or 22%.
Table 1—Definitions of Asthma
|Ciba Foundation Guest Symposium||“Asthma refers to the condition of subjects with widespread narrowing of the bronchial airways, which changes its severity over short periods of time either spontaneously or under treatment….”|
|American Thoracic Society||“Asthma is a disease characterized by an increased responsiveness of the trachea and bronchi to various stimuli and manifested by a widespread narrowing of the airways that changes in severity either spontaneously or as a result of therapy.”|
|American College of Chest Physicians, American Thoracic Society||“A disease characterized by increased responsiveness of the airways to various stimuli and manifested by slowing of forced expiration which changes in severity either spontaneously or as a result of therapy.”|
|World Health Organization||“…a chronic condition characterized by recurrent bronchospasm resulting from a tendency to develop reversible narrowing of the airway lumina in response to stimuli of a level of intensity not inducing such narrowing in most individuals.”|
Tags: Airway responsiveness, Asthma, bronchial responsiveness, lung function, smoking